Live attenuated coccidiosis vaccine: selection of a second precocious line of Eimeria maxima.

An attenuated line (CP) of Eimeria maxima was obtained by selection for early development of oocysts. Despite a small reproductive potential the CP line was highly immunogenic against its parent but did not completely protect chickens against challenge with virulent heterologous strains. However, in combination with another attenuated line with similar characteristics, good protection was induced.